Th e Public Switched Network (PSN) provides critical commercial telecommunications services and National Security and Emergency Preparedness (NSEP).  Telecommunication Service providers, qequipment manufacturers, users, and the Federal Government are concerned that vulnerabilities in the PSN could be exploited and result in disruptions or degradation of service.  To address these threats, the National Institute of Standards and Technology (NIST) is collaborating with Bellcore to investigate the vulnerabilities and related security issues that result from the use of open systems architectures in the telecommunications industry.  Security features required to counter the threats are identified. This guideline focuses on two specific components of a Telecommunications Management Network (TMN) - Network Elements (NEs) and Mediation Devices (MDs) - with emphasis on the security features needed to protect the Operations, Administration, Maintenance, and Provisioning (OaM&P) of these components. this document is intended to provide a security baseline for NEs and MDs that is based on commercial security needs.  Inaddittion, some National Security and Emergency Preparedness (NS/EP) security requirements will be integrated into the baseline to address specific netwrk security needs. The guideline should assist telecommunications vendors in developing systems and service providers in implementing systems with appropriate security for integration into the PSN.  It can also be used by a government agency or a commercial organization to formulate a specific security policy.  It does not stipulate regulatory requirements or mandated standards of the National Institute of Standards and Technology.